1. Field of the Invention
This invention relates generally to completion and production strings and more particularly to spooled coiled tubing strings having devices and sensors assembled in the string and tested at the surface prior to their deployment in the wellbores.
2. Background of the Art
To obtain hydrocarbons from the earth subsurface formations ("reservoirs") wellbores or boreholes are drilled into the reservoir. The wellbore is completed to flow the hydrocarbons from the reservoirs to the surface through the wellbore. To complete the wellbore, a casing is typically placed in the wellbore. The casing and the wellbore are perforated at desired depths to allow the hydrocarbons to flow from the reservoir to the wellbore. Devices such as sliding sleeves, packers, anchors, fluid flow control devices and a variety of sensors are installed in or on the casing. Such wellbores are referred to as the "cased holes." For the purpose of this invention, the casing with the associated devices is referred to as the completion string. Additional tubings, flow control devices and sensors are sometimes installed in the casing to control the fluid flow to the surface. Such tubings along with the associated devices are referred to as the "production strings". An electric submersible pump (ESP) is installed in the wellbore to aid the lifting of the hydrocarbons to the surface when the downhole pressure is not sufficient to provide lift to the fluid. Alternatively, the well, at least partially, may be completed without the casing by installing the desired devices and sensors in the uncased or open hole. Such completions are referred to as the "open hole" completions. A string may also be configured to perform the functions of both the completion string and the production string.
Coiled tubing is often used as the tubing for the completion and/or production strings. The coiled tubing is transported to the well site on spools or reels and the devices that cause upsets in the tubing are integrated into the coiled tubing at the well site as it is deployed into the wellbore. Spooled coiled tubing strings with integrated devices have been proposed. Such strings can be assembled at the factory and deployed in the wellbore without additional assembly at the well site. However, the prior art proposed spooled coiled tubing strings require that there be no "upsets" of the outer diameter of the coiled tubing, i.e., the devices integrated into the coiled tubing must be placed inside the coiled tubing or that their outer surfaces be flush with the outer diameter of the coiled tubing. Such limitations have been considered necessary by the prior art because coiled tubings are inserted and retrieved from the wellbores by injector heads, which are typically designed to handle coiled tubings of uniform outer dimensions. In many oilfield applications, it is not feasible or practical to avoid upsets because the gap between the coiled tubing and the borehole wall or the casing may be too large for efficient use of certain devices such as packers and anchors or because of other design and safety considerations. Also, limiting the outer diameter of the devices to the coiled tubing diameter will require designing new devices.
Additionally, the prior art coiled tubing strings do not include sensors required for determining the operation and health (condition) of the various devices and sensors in the string, or controllers downhole and/or at the surface for operating the downhole devices, for monitoring production from the wellbore and for monitoring the wellbore and reservoir conditions during the life of the wellbore. The prior art spooled coiled tubing strings do not provide mechanisms for testing the devices and sensors from an end of the tubing at the surface before the deployment of the string in the wellbore. Completely assembling the string with desired devices and sensors and having mechanisms to test the operations of the devices and the sensors at the factory prior to the deployment of the string in the wellbore can substantially increase the quality and reliability of the such strings and reduce the deployment and retrieval time.
A specific type of coiled tubing, referred to "electro-coiled-tubing" (ECT), contains high power cable, data communication lines or links and hydraulic lines inside the coiled tubing. An ECT is attached to a downhole electrical submersible pump (ESP) with a lower coiled tubing adapter and to the wellhead with an upper coiled tubing adapter. These adapters are installed on the coiled tubing at the well site, typically at the work area below the tubing injector. The lower adapter is assembled on the ECT immediately after the ESP and related equipment has been prepared and hung off in the well. Commercially available adapters are relatively complex devices. They contain fairly complex electrical penetrators (also sometimes referred to as "feed through") along with associated cable connectors which carry electrical power form the ESP power cable across a pressure transition region into the motor and seal section. During deployment of the ECT in the well, if the ECT is not filled with a fluid, it creates a large differential pressure between the wellbore and the inside of the ECT. The penetrator in the lower adapter isolates the inside of the ECT from the wellbore pressure. The lower adapter also includes passages for hydraulic lines and instrument lines and a shear subassembly that can be broken in case the system gets stuck in the well. Installing a lower adapter on the ECT at the well site is a relatively complex and time consuming process. Sophisticated electronic devices, sensors and fiber optic cables and devices are now being used or have been proposed for use in electro-coiledtubings. It is highly desirable to assemble and fully test such ECTs prior to transporting them to the wellsite.
After attaching the lower adapter, the ECT carrying the ESP and associated equipment is run into the well with the tubing injector to the desired location (depth). The upper coiled tubing adapter is then attached to the ECT. As with the lower adapter, the upper adapter also contains an electrical penetrator, various connectors, hydraulic lines and conductors or wires. The upper adapter is then attached to a tubing hanger which is then lowered into the wellhead equipment to support the ECT in the well. Assembly of the upper adapter also is very complex and time consuming. Completely testing the ECT after installing the upper and lower adapters at the well site is not feasible or possible. Thus, it is desirable to install and test all such devices at the factory, which is a relatively clean environment and is conducive to performing rigorous testing of the assembled systems.
The present invention provides spooled coiled tubing strings which include the desired devices and sensors and wherein the devices may cause upsets in the coiled tubing. The string is assembled and tested at the factory and transported to the well site on spools and deployed into the wellbore by an injector head system designed to accommodate upsets in the tubing strings. The strings of the present invention may be completion strings, production strings and may be deployed in open or cased holes. This invention also provides methods for installing and testing an ECT at the surface prior to transporting them to the well site. The ESP can be installed at the factory or at the well site.